(1) Field of the Invention
The present invention relates to a temperature responsive device for an internal combustion engine to automatically control temperature of intake air to be supplied to the engine, and more particulary relates to an improved construction of a thermostatic valve having dual functions, one of which is to supply air to a slow-port passage of a carburetor in response to the temperature of the engine or an air cleaner so as to prevent excessive richness of an air-fuel mixture to be fed to the engine and the other of which is to control a negative pressure motor in response to the above engine temperature, the negative pressure motor proceeding a switching operation for introducing warmed air into the carburetor through the air cleaner and a control of the amount of the warmed air.
(2) Description of Prior Art
In a conventional thermostatic device for an internal combustion engine, a thermostatic valve is provided to detect temperature of intake air during a time when the temperature of the ambient air is cold especially during a winter season and to actuate a negative pressure motor as a function of the detected temperature so as to introduce warmed air to the engine, and another thermostatic valve is provided to introduce additional air into an intake manifold for the purpose of preventing an extreme richness of an air-fuel mixture fed to the engine during a time when the ambient temperature is relatively high, especially during a summer season.
The conventional thermostatic device just described is disadvantageous in view of necessity of two kinds of thermostatic valves, complicated pipe lines for communicating the thermostatic valves with the associated portions such as the intake manifold, the carburetor and so on in an automotive engine compartment, and its high cost.
In another well-known thermostatic device of this kind, for example disclosed in U.S. Pat. No. 3,394,687, in which one valve is employed to proceed the above dual functions, a valve member is slidably but sealingly disposed in a valve housing being actuated to move down-and-upwardly by a temperature responsive expanding material such as wax, the down-and-upward movement of the valve member controlling both the amount of warmed air supplied to an engine through a carburetor and the amount of additional air fed to the engine. The thermostatic valve has, however a disadvantage that a reliable operation may not be ensured for a long time since clearance between the outer surface of the valve member and the surrounding inner surface of the valve housing for the valve member becomes larger as it is used.